Hey Spy!
I have two agents and neither are the most exemplary communicators if we're not actively working on a deal. It goes in spurts. Like this--
I'll e-mail agent an idea I'm working on. He'll call or e-mail to tell me what he thinks. Assuming he thinks it's a good idea, I'll go off and work on the proposal. When I've finished a first draft of the proposal, I send it to him for comments. If it needs improvement, he makes suggestions, and I revise. When it's done, he lets me know where he's going to send it. As responses come in, he calls to tell me what those responses are.
When an offer comes in, we're usually on the phone a couple of times a day until a deal is finalized.
Then a long stretch may pass while I'm off working on the project, and we may not speak again until I'm just about done and ready for a new deal.
If I have any problems along the way, I e-mail him. Sometimes he'll conference in on a call I have with an editor or publicist.
And sometimes we just check in briefly to chit-chat a bit or for me to ask for career advice.
But back to your original question, I assume that you've just signed a deal with an agent and are now waiting for some kind of communication? It should happen quickly, assuming the agent has something of yours to submit. He/she should be in contact with you to tell you what the plan is and where it's headed within about a week or two of contract signing, I'd think. If not, time for you to make a call to check in.